Wireless receiving system



Z l 4.D

i 2 LU 3 /QSDV L. ESPENSCHIED.

WIRELESS RECEIVING SYSTEM.

APPLICATION FILED MAY15,1916.

Patented Dec. 21,1920.

Inventar UNITED STATES 'marismas PATENT OFFICE.

LLOYD ESPENSCHIED, OF HOLLIS, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

WIRELESS RECEIVING SYSTEM.

T all 'whom it may concern:

Be it known that I, LLOYD EsrnNsCHinD,

l residing at Hollis, Long Island, in the county of Queens and State ofNew York, have invented certain Improvements in Wireless ReceivingSystems, of which the following is a specification.

My invention relates to a wireless signaling system and moreparticularly to a system for the reception of wireless signals. Itsobject is to provide a receiving system in which the receivinginstrument shall be pro-f. tected from disturbing oscillations, such asthose due to atmospheric or static disturbances, which might interferewith the efiicient receipt of signals. The invention finds its use inconnection with a wireless tele- O'ra h or tele hone s stein.

D Itp ism toythose acquainted with the art that atmospheric or staticinterference constitutes a very serious menace to the satisfactoryreception of wireless messages and that the elimination of saidinterference -is a problem of great difliculty. This difliculty inheresin the fact that the frequency to which the receiving system in tuned,and is therefore most responsive, is very closely the same as thefrequency of the natural oscillations set up bythe incidence of anatmospheric disturbance on the receiving antenna. The naturaloscillations are therefore of substantially the frequency to moststrongly affect the receiving device, and cannot be eliminated by timingas can persistent disturbances -from a foreign station.

This invention contemplates an arrangement by which the receiving devicein addition to being operatively connected to the receiving antenna isalso connected to an auxiliary circuit which simulates the receivingantenna as regards natural oscillations, means being provided forexciting natural oscillations in said auxiliary circuit simultaneouslywith the excitation of natural oscillations in the receiving antenna bytransient disturbances.

My invention is best understood by reference to the accompanyingdrawings in which Figures 1 and 2 are diagrams of wireless receivingsystems embodying arrangements of m invention.

eferring to Fig. 1, 1 is a receiving antenna, tuned by means ofcondenser 2 and inductance 3 to resonance with the waves it is desiredto receive. A receiving system Specification of Letters Patent.

Patented Dec. 21, 1920.

1916. serial No. 97,566.

comprising a resonant receiving circuit 4, a detector 5, and a receivingdevice 6 is connected to antenna 1. The detector 5, preferably of thevacuum tube type has its input side connected to resonant receivingcircuit 4, and its output side connected to receiver 6. Receivingcircuit 4 is resonant to the receiving frequency. 7 is an auxiliaryantenna preferably aperiodic. Across an impedance element 8,r which maybe a non-inductive resistance element, and which is in series withantenna 7 is connected to the input side of an ampliiier 9, preferablyof the vacuum tubetype. To the output side of amplifier 9 is coupled,preferably very loosely, an oscillation circuit 10 which is alsoconnected to the resonant receiving circuit 4. Circuit 10 containsresistance, ca-

pacity, and inductance elements which'are to be given such values thatsaid oscillation circuit 10 'has the same natural periodicity as antenna1, and also the saine characteristic damping factor. When this conditionis satisfied the natural oscillations executed by oscillation circuit 10when excited by an impulsive disturbance are similar to those executedunder like conditions by antenna-1. The connections of antenna 1 andoscillation circuit 10 to circuit 4 are differential and thereforesimultaneous oscillations in antenna 1 and oscillation circuit 10 opposeand tend to neutralize with respect to receiving circuit 4.

The operation of the organization shown in Fig. 1 in protecting receiver6 from interference will now be readily understood. When the system isreceiving relatively sustained oscillations of the frequency to whichantenna 1 and receiving circuit 4 are attuned, antenna 7 is unresponsiveand consequently oscillation circuit 10 is not energized. The receptionof signals is therefore unaffected by the auxiliary arrangement whosefunction is exclusively to reduce interference. When, however, anatmospheric or arbitrary disturbance strikes antenna 1 it simultaneouslystrikes antenna 7 and both antennae are excited. Antenna 1 executescharacteristic damped oscillations while antenna 7 impresses animpulsive potential difference across the input circuit of amplifier 9.As a consequence oscillation circuit 10 is impulsively excited andexecutes characteristic damped oscillations of the same periodicity anddamping as those simultaneously from the antenna 7 are distorted so asto present steeper wave fronts which increases the transient orimpulsive excitation of the oscillation circuit 10. Receiving circuit 4is therefore excited by oscillations of the same form in antenna 1 andoscillation circuit 10 respectively and in consequence of differentialconnection said oscillations oppose and tend to neutralize. Since themagnitude of the oscillations excuted by oscillation circuit 10 iscontrollable by the amplifying power of amplifier 9, proper adjustmentof said amplifying power will make the resultant induction in receivingcircuit 4 substantially zero. Said resultant induction may also bevaried and reduced to practically zero value by adjustment of therelative connections between receiving circuit 4 and antenna .1, andbetween receiving circuit 4 and osc1llation circuit 10 respectively. i D

Fig. 2 is an arrangement mcorporatmg the same fundamental principle inan organization employing a single antenna. This arrangement isparticularly adapted to a system for the reception of undamped waves ofa definite frequency. Referring to Fig. 2, 21 is a receiving antennatuned to the frequency of the signals to be received. Antenna 21includes an inductance coil 22 and a condenser 23 adjusted so that theirjoint serial impedance at the frequency` of reception is zero. Anon-inductive resistance 24 is connected in parallel with inductance 22and condenser 23 and across the terminals of said resistance isconnected the input side of an amplifier 25, preferably of the vacuumtube t-ype. The function of non-inductive resistance 24 is merely toprovide a conductive path between filament and grid of said amplifier.Connected to output circuit 26 of amplifier 25 is oscillation circuit27, said oscillation circuit containing resistance inductance andcapacity elements so adjusted that the natural oscillationscharacteristic of said circuit are of the same frequency and damping asthose characteristic of antenna 21. Resonant receiving circuit 28 isdifferentially connected to antenna 21 and oscillation circuit 27. Areceiving device 29 is connected to receiving circuit 28 through adetector 30, preferably of the vacuum tube t e. yl'1`he operation of theorganization of Fig. 2 will be readily understood in the light of theexplanation of the operation of that of Fig. 1. lfVhen continuous wavesof the contemplated frequency are being received the potentialdifference across the terminals of resistance 24 is Zero in consequenceof the fact that inductance 22 and condenser 23 are serially resonant atthis frequency. Oscillation circuit 27 is therefore not excited throughamplifier 25. When a transient or arbitrary disturbance strikes antenna21, amplifier 25 and therefore oscillation cirn cuit 27 are impulsivelyexcited, oscillation circuit 27 oscillating in the same manner asantenna 21. The natural oscillations in antenna 21 and oscillationcircuit 27 oppose with respect to the receiving circuit and by a properadjustment of connections and amplifying power they may be made toneutralize approximately completely My invention will be-seen to bedirected broadly to reducing interference by providing an oscillationcircuit simulating the receiving antenna as regards naturaloscillations, differentially connecting a receiving circuit to thereceiving antenna and to said simulative circuit, providing means forexciting natural oscillations in said simulative circuit simultaneouslywith the natural oscillations excited in the receiving antenna, andproviding means for controlling the magnitude of the naturaloscillations in said simulative circuit.

That is claimed is:

1. A wireless system comprising a receiving antenna; a shock excitedoscillation circuit having the same periodicity and dampingcharacteristic as said antenna; a receiving device; connections betweensaid receiving device and said antenna and between said receiving deviceand said oscillation circuit adapted to oppose the current from saidantenna against the current from said oscillation circuit; and means forsubstantially equalizing the amplitude of the natural oscillations insaid oscillation circuit and in said antenna.

2. A wireless system comprising a receiving antenna; a shock excitedoscillation circuit having the same periodicity and dampingcharacteristic as said antenna; a receiving device connected to saidantenna and said oscillation circuit so as to oppose the current fromsaid antenna against the current from said oscillation circuit; meansfor rendering said oscillation circuit unresponsive to sustained wavesof the frequency of those it is desired to receive; an aperiodicauxiliary antenna for exciting natural oscillations in said oscillationcircuit simultaneously with the excitation of natural oscillations insaid receiving antenna and for controlling the relative amplitude of thenatural oscillations in said oscillation circuit.

3. A wireless system comprising a receiving antenna, a receiving systemconnected with said antenna, an oscillation circuit having the samenatural periodicity and damping characteristic as said antenna, saidoscillation circuit being associated with said receiving system, and anaperiodic antenna operative when said receiving antenna oscillates inresponse to a natural disturbance I to produce neutralizing oscillationsby shock excitation in said oscillation circuit, whereby said receivingsystem is unaffected by such disturbances.

4. A wireless system comprising a receiving antenna, a receiving systemconnected with said receiving antenna, an auxiliary aperiodic antenna,and an oscillation circuit having the same periodicity and dampingcharacteristic as said receiving antenna and associated with saidreceiving system and said auxiliary antenna.

5. A wireless system comprising a receiving antenna, a receiving systemconnected therewith, an oscillation circuit associated with saidreceiving system, and an auxiliary aperiodic antenna associated withsaid osi' cillation circuit operating in response to naturaldisturbances to set up oscillations by shock excitation in saidoscillation circuit when said auxiliary antenna responds to naturaldisturbances, to neutralize the effect of the receiving antenna naturaloscillations upon said receiving system.

6. A wireless system comprising a receiving antenna, a receiving systemconnected therewith, an oscillation circuit, said antenna andoscillation circuit having the same periodicity and dampingcharacteristics, aperiodic means unresponsive to signaling frequenciesassociated with said oscillation circuit, said means operating inresponse toy natural disturbances to set up oscillations by shockexcitation in said oscillation cir,- cuit, and a distortionlessamplifier to equalize the amplitude of the oscillations of the saidoscillatory circuit and the natural oscillations of the said receivingantenna, whereby the effect of said disturbances with respect to saidreceiving system may be substantially eliminated.

7. A wireless system comprising a receiving antenna tuned to receptionfrequency, an auxiliary aperiodic antenna, an oscillation circuit havingthe same periodicity and damping characteristics as said receivinantenna and adapted to be shock excited by said auxiliary antenna, aresonant receiving system connected with said receiving antenna and alsowith said oscillation circuit, the latter connection being differentialwhereby the natural oscillations set up in said receiving system by saidreceiving antenna may be substantially neutralized by the oscillationsset up in said receiving system by the said oscillation circuit whenexcited by impulses from said auxiliary antenna.

8.In wireless signaling systems, the method for suppressing staticinterference which consists in permitting static impulses to beimpressed on a tuned antenna and an aperiodic antenna amplifying theimpulses from said aperiodic antenna, producing by the said amplifiedimpulses shock excited oscillations having the same natural periodicityand damping characteristic as those oscillations to which said. tunedantenna is resonant, and impressing the natural oscillations from saidtuned antenna and the said shock excited oscillations upon a receivingcircuit in such manner that the two sets of oscillations will be opposedand neutralized.

9. In a wireless signaling system, the method for suppressing staticinterference which consists in permitting static impulses to beimpressed on a tuned antenna and an aperiodic antenna, producing by theimpulses of the said aperiodic antenna shock excited oscillations havingthe same periodicity and damping characteristic as the naturaloscillations to which the said tuned antenna is resonant, and impressingthe natural Ioscillations from said tuned antenna and the shock excitedoscillations upon a receiving circuit in such manner that the two setsof oscillations will be opposed and neutralized.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses, this 4th day of May 1916.

LLOYD ESPENSiCI-IIED.

Witnesses:

RALPH W. WOLF, FREDK. S. ROBINSON.

